Commodore Plus 4 - Page 166

MORE ON
GRAPHIC
STATEMENTS
There are a few concepts that apply to all of the bit map graphics
statements. First is the concept of the Pixel Cursor (PC). The PC is
similar to the cursor in text mode; it is the position where the next dot
is to be drawn. Unlike the text cursor, the PC is invisible. All drawing
commands use the PC. In addition, the locate command allows you
to reposition the PC without drawing anything.
Wherever you would use X,Y coordinates in a drawing command,
you can use RELATIVE coordinates instead. Relative coordinates are
based on the current value of the PC To use relative coordinates, just
place a + or - in front of your coordinates. A plus sign before the X
value moves the PC to the right. A minus sign before the X value moves
the PC to the left. Similarly, a minus sign before the Y coordinate moves
the PC up, while a plus sign moves the PC down. For example:
LOCATE +100,-25
DRAWl, + 10, + 10TO100,100
moves the PC right
100 pixels and up 25.
draws a line 10 pixels
right and 10 pixels
below the current
value of the PC to the
absolute point 100,100.
You can also specify a distance and an angle relative to the current
PC by separating the two parameters by a semicolon.
For example:
LOCATE 50;45
moves the PC from
its current location
by a distance of 50
dots at an angle of
45 degrees.
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